1. Field of the Invention
The present invention relates to haymaking machines for tedding and windrowing crop material such as hay. More precisely, the invention is concerned with hay-making machines of the type comprising one or more rotors which are rotatably mounted about generally upright axes and which are provided with a plurality of crop working elements in the form of flexible tines.
2. Description of the Prior Art
In the haymaking process, crop material usually has to be turned or tedded once or more for proper drying after it has been cut with either a mower or mower-conditioner. Also, prior to being baled, dried crop material has to be raked together in windrows. Single purpose tedding and raking machines are generally known in the art and usually are capable of doing an excellent job. However, single purpose machines have an important drawback in as much as to make good quality hay, two different types of such machines are required, namely a tedder and a rake. Obviously this can make haymaking more expensive and frequent interchange between tractor-mounted machines may be necessary.
Combined machines capable of both raking and tedding crop material (hereinafter called "rake tedders") have gained acceptance mainly as an economical means for accomplishing both jobs. This is especially true in the more humid European countries where hay must be turned and moved more frequently for proper drying. One particular type of rake-tedder is the "cam-actuated" type in which a cam is used in conjunction with a follower to actuate a plurality of equally spaced tine bars that extend radially outwardly from a rotor. As the tine bars cycle with the rotor, the cam follower engages the cam and cause the tine bars to rotate about their axes, causing the tines which extend from the outer ends of the tine bars gradually to move from a crop-engaging position to a raised, crop-releasing position. The cam may have such a profile and be made adjustable that either raking or tedding may be accomplished. The cam is made adjustable so that the position at which the tines release the crop is variable relative to the rotors and direction of travel of the rake-tedder.
In performing the raking operation the tines sweeep an entire swath of crop material into a windrow and then rise, so releasing the crop which is thus deposited in a narrow windrow extending between two laterally spaced rotors. For the tedding operation, the cam is adjusted such that the tines engage the crop material and sweep it outwardly from the centre of the machine spreading it over about the same width as the original swath. In using a double rotor rake-tedder for raking it has been found that a slower rotational speed must be used so as to form an acceptable windrow. Thus to optimise the efficiency of the rake-tedder, it is desirable to provide it with a two-speed input drive means, one input drive being slower than the other to accommodate raking, whilst the faster speed is employed for tedding. Usually, machines of this type accomplish excellent windrowing but leave room for improvement as regards tedding.
For tedding, it is desirable to obtain a much more vigorous action of the tines on the crop material than is the case for windrowing. This is partially obtained with the machine described above by rotating the rotors at a higher speed. In addition, it is desirable to arrange for the tines not to retract from the crop material during operation.
In another prior art machine, this same result is obtained by withdrawing the cam follower from the cam firmly securing the tine bars to the rotor framework, whereby the tine bars are no longer rotated about their longitudinal axes. A drawback of this arrangement is that the tine bars individually must be brought into the tedding position and immobilised in this position. This is time-consuming and it may happen that the operator forgets to reposition and immobilise one or more tine bars which results in the machine malfunctioning. Furthermore, the tines which are left rotating may hit other tines thus causing damage to the machine. Also this repositioning of the tine bars from the tedding position into the windrowing position and vice versa necessitates delicate adjustments.
In another prior art machine of the type described above, the cam follower is urged against the cam by spring means. The tine bars can be brought from the windrowing position into the tedding position by a downward shifting of the cam until the cam follower is out of engagement with the cam. An important drawback with this machine is that in order to bring the machine from the windrowing position to the tedding position and vice versa, it is necessary for the cam to be moved axially along a central shaft. This is disadvantageous because the position of the cam and its rigidity in relation to its support axis determine the trajectory described by the tines during windrowing, and thus the quality of the windrowing performance. Furthermore, the spring means which urge the cam follower into engagement with the cam are continuously stretched and released during operation. This may result in a rapid fatigue of the spring means followed by an appreciable reduction of the quality of machine performance, particularly during the tedding operation when the crop material to be displaced is green and heavy. Also, premature breakdowns may occur.
In all of the above described prior art arrangements the cam follower is in the form of a roller rotatably mounted on a tine bar via crank means. In practice it has been experienced that these cam rollers are fast wearing components which are difficult to design for a longer life without making the cost of manufacture prohibitive. This is a problem which is inherent to the principle of cam-actuated tine bars since the cam follower is moved up-and-down once per cycle of the rotor and as the latter has to be rotated at a relatively high speed, the cam follower is moved up-and-down very abruptly at a corresponding high frequency. This results not only in considerable vibration but also in constant movement relative to the cam.
Other machines have been conceived wherein the tines are pivotably mounted on the rotors and are arranged to move radially outwardly against spring forces under the influence of centrifugal forces. Rake-tedders of this type unquestionably have better tedding characteristics but the windrowing characteristics are less satisfactory. When changing over from the tedding condition to a windrowing condition, the tines must still be adjusted individually and in addition to that, windrow deflectors must be brought into position. Apart from the foregoing drawbacks this type of rake-tedder is simple in design.
Other rake-tedders have been conceived with a view to providing universal machines having both excellent tedding and raking characteristics. Such machines have turned out to be very complicated in design and difficult to adjust. Furthermore such machines usually are relatively expensive.